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R. C. MATHES. AMPLIFYING AND CORRECTING SYSTEM. APPLICATION FILED AUG.I4. 1918.

1,3 1 1,283. Patent-ed July 29, 1919.

3 SHEETS-SHEET 1- hi t-Emil R. C. MAYHES. AMPLIFYING AND CORRECTING SYSTEM. APPLICATION FILED AUG.14, 19H].

Patented July 29, 1919.

3 SHEETSSHEET 2- F iI F R. C. MATHES.

AMPLIFYING AND CORRECTING SYSTEM. APPLICATION FILED AUG.I4. I918.

1,31 1,283. Patented July 29, 1919 3 SHEETS-SHEET 3- fiyzki HIIIIIIFEM outrun STATES PATENT.

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ROBERT C. MATHES, OF NEW YORK, N. Y ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NTEW YORK, N. Y., A CORPORATION' OF YORK.

AMPLIFY'ING AND coanno'rme SYSTEM.

Specification of Letters Patent.

Patented July 2a, 1919.

' Application filed August 14, 1918. SerialNo. 249,828.

To all whom it may concern;

Beit known that I, ROBERT C. MArHE's, a citizen of the United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in Amplifying and Correcting Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to amplifying and correcting systems. It is particularly concerned with systems suitable for use'in connection with telegraphic signaling overconductors of high capacity such as submarine cables. 7

It is well known thatwhen signals are transmitted over high capacity conductors,

the original wave form of the signals. is

destroyed, and the wave form of the received signal often bears very little resemblance to the original transmitted wave. In a copending application, Serial No. 240,792, filed June 19, 1918, I have shown how, by using correcting net-works at the receiving end of the cable, it is possible to diiferentiate the received wave, and to recombine the various 4 derivatives; to make available for the actuation of the recei'vlng instrument, a current having awave form closely approximatingthat of the transmitted signal. In the said application it was also shown how amplifiers might be used to increase the power value of such corrected waves wane extent required for effective operation of the receiving instrument, .or .for retransmission to another telegraph conductor.

The present invention has for its object to facilitate the separation" of the various derivatives and their recombination. in proper proportions to give the desired synthetic curve. To this end the invention provides that instead of amplifying the ar rival'curve and the several derivative curves in one amplifying system, these various components are separated out and amplified to the desired degree, in separate and distinct amplifying systems, and are then combined,

, after amplification, in a common output or work circuit The invention will be more clearly understood by reference to the aocompanying' drawings, in which Figure 1 gives a diagrammatic representation of a system arranged to ampllfy the main arrival curve and thederivatives thereof, each in a separate system;. F1g.- 2 shows a modlfication of the. arrangement of Fig. 1 using a seriescombination of the output circuits and also a partial series connection of the input circuits of the various amplifier sys tems; and Fig. 3 shows a further modification wherein by the use of more complicated .correctingnet-works two or more of the component wavesmay be amplified-together in a single system.

Referring to Fig. 1, 1 represents a telegraph conductor, in this case a submarine cable, terminating in a duplex net-work comprising the two ratio arms 2 and 3, and the artificial line 4. The apex of the network is connected to the usual transmitting key 5. Bridged across the net-work in the position of the-usual receiving device is the primary winding 6 of the transformer 7. The secondary winding 8 of the transformer 7 is connected to an amplifier system A, here illustrated as a two-stage system employing thermionic amplifiers 9 and 10. These amplifiers have the usual'filamentary cathodes 11, input or gridelectrodes-12 and output electrodes 13. The filaments 11 are heated by current supplied from a battery 14. The output electrodes 13 are maintained positive with respect to the filaments 11, by means of a battery 15. The amplifier system A is' here arranged and the transformer 7 is designed to transmit and to amplify the main arrival curve only, or a wave conforming very closely to it. Any transformer inserted in the circuit in this way has a differentiating action and produces in its secondary winding, a current whose form is that of a derivatlve of the prlmary current,

so that normally the introduction of the transformer 7 in the position shown would pass on to the amplifier system A a current which was the derivative of the arrival curve, and the arrival curve itself would be to a large extent, if not entirely, lost. In

order that the arrival curve may be retained and thus perform its function in keeping up the tail of the synthetic wave, the transformer? should have a relatively high time constant, andthe shunt on the primary 6 comprising the ratio arms 2 and 3 should be relatively low in impedance. Thus by the proper selection of the trans: former and shunting elements, the amplifier 9,may have applied to it a current wave whichmay be an ap roximate duplicate of the arrival curve, he output of the amsistance 22.

plifier system A may be adjusted by means of the potentiometer 21 and the variable re- The resistance 22 has the further function of preventing the outputs of the other systems being fed back into the output circuit of the element 10, and thus varying its amplifying powen from moment to moment. A. portion of the output of the amplifier 9 is, however, applied by means, of conductors 23 and 24 to the input circuit of an amplifier system B,

com-

- posed, in this case, of two thermionic amwhich are connected in 'plifiers-25 and 26. Locatedintermediate the amplifiers 25 and 26 is a transformer 36.

This transformer will have a differentiating action upon the current applied to it and will produce across the input circuit of theamplifier 26, a voltage having a wave form corresponding to the first derivative of the voltage applied to the input circuit of amplifier 25; This first derivative current will be amplified in the amplifier 26 and the desired proportion of it, to be added to the ultimate synthetic wave may be obtained by a proper adjustment of the amplifier or by the variable resistance 32 or by both.

Similarly, afurther amplifying system C may be arranged to produce and to add a proper amount of a current wave having and 3l;of a common output circuit, to actuate a recording device 35," or for retransmission over another telegraph conductor, which may be either a land line or submarine cable.

The alternative arrangement of Fig. 2

differs only slightly from that of Fig.1-

butillustrates how if desired the input circuits-of the various amplifier systems, as well astheir output circuits, may be connected in series rather ,than in parallel. Here the input circuits and B are connected to the cable circuit through transformers 7, theprimaries 6 of series in the. cable circuit. The output circuits of the amplifier systems A, B and C, are" similarly con-' nected through transformers 37, to a com- 'mon output circuit, the secondary winding of said transformers being connected in series with the receiving device 35as shown. It will be obvious that any series, parallel or series-parallel arrangement of the output and in ut circuits maybe used without departing rom the spirit and scope of the invention andthat the particular arrangement to be employed will in general be ber of amplifying systems.

ofrboth systems A the specific service requirements bridged across the line and a capacity 29 shunted by resistance 30 in series with the line. This net-work is of a form described in my .copending application above referred to and need not be described in detail here.

It is' sufiicient to note that such a net-work, while producing one or more derivatives of the voltage or current wave applied to it, also passes along a portion of the applied wave and thus delivers to its output circuit a combination wave composed of the impressed wave and one or more derivatives thereof the proportions of the different components being dependent upon the values of the different elements employed. In the case illustrated in Fig. 2 amplifiei systems A and B. would therefore (as in the arrangement of Fig. 1) produce in the common output circuit current waves having the forms of the arrival curve and its first derivative respectively, while amplifier sys-' tem C, instead of producing a current corresponding to the second derivative alone willproduce a complex wave in which the second derivative predominates or inwhich the second and third derivatives are present in anydesired ratio depending ,upon the value of the inductances, resistances and capacity used. The use of such a correcting net-work is of advantage where it is desired to obtain a number of the higher derivatives without unduly multiplying the num- This idea is carried further in the system illustrated 'in F ig.- 3. Here, for example,

' the primary 6 of transformer 7 is shunted by an inductance l6 and resistance 18 in series, whllea condenser 19 shunted by resistance 20 placed in series wlth the primary 6. This net-work has the effect of 'addingva first derivative to the arrival curve .so that amplifier system A produces-in its output circuit "a combination of these two components.

The condenser 17 shunting resistance 18 aids in maintaining the original form of the arrival curve and therefore helps to keep upthe tail of the ultimate synthetic wave.

Similarly amplifier system B, by employing a net-work composed, for example," of

inductances 27, resistances 2S and 30 and capaci'ty 29,as shown, maybe made to produce in the common output circuit a complex wave whose main component corresponds to a combinationjof the second, and third def rivatives of the arrival cur e.

component made up of a combination ofthe Amplifier system C may in a similar'manner be made to produce a predominating fourth and fifth derivatives. Thus with only three amplifier systems it is possible to produce the first five derivatives of the arrival curve and to combine these six components in proper proportions in the common work circuit. It will be understood that the arrangement of Fig. 3 is somewhat less exact than that of Fig. 1, for example, and that is in the nature of'a compromise between the latter arrangement and that disclosed in my copending application above referred to.

It will be noted that in passing through any vacuum tube element the polarity of the transmitted signal changes; that is, considering the element 9, if we apply a signal such that the polarity between the grid 12 and the filament 11 is changed from zero to positive, the potential between the plate 13 and the filament 11 will be changing so as to make the plate relatively more negative with respect to the filament. It will, therefore, be seen that the component corresponding to any one of the amplifier systems may be fed in either of two phases, according to the number of vacuum tube elements used in that system. Of course, where transformers are 1 employed as in Figs. 1 or 2, the phases may also be reversed by interchangin the transformer connections. In Fig. 3, far instance,

where suchreversal of phase. through the use of transformers is not possible, it will be noted that the component wave of channel B feeds into the output circuit in what may be considered reverse phase from channels A and C. It may equally well be fed-into the output circuit in like phase by adding an additional vacuum tube element between element 26 and the common output circuit.

The same fundamental principle is, how- 'ever, seen to be present in each of the three of the modifications here used as illustrative of the invention, namelythe use of a separate amplifying system for each of the dominating components which are intended to play their respective parts in determining the form of the ultimate synthetic wave to be used in the work circuit. Another feature present in the system and one which was also emphasized in the copending appli cation above referred to is the arrangement whereby each correcting net-work or transformer is separated from the preceding 5 ing unilateral conductivity. This makes it impossible for one net-work to react on the preceding one and makes possible the design of each net-work or transformer without reference to any other net-work in the system. vWhat is claimed is: 1. The method of combining with an electric wave of given form, other derived waves of different forms so as to produce a resultant wave of a desired form which consists in separating out the various component waves amplifying them separately to the desire degree, and recombining the separately amplified waves to actuate a common receiving device. I

' 2.'The method of operating a signal responsive device which consists in deriving from the received current wave other ourrents each having a distinct wave form, am-

plifying each of said currents separately in a separate circuit and subjecting said responsive device to the conj oint action of said amplified currents.

3. In combination with a signaling conductor, means for producing from the currents arriving over said conductor, other currents difi'ering therefrom. and from each other in Wave form, separate circuits on which the several currents are respectively impressed, means in each se arate circuit for-amplifying the currents t erein, and a receivingdevice responsive to said amplified currents ointly.

4. The combination with a signaling conductor, a responsive device connected thereto for indicating the arrival of currents from said conductor, means intermediate said conductor and said device for amplifying said arrival current, means for deriving from said arrival current another current difi'erin in wave form therefrom, separate means or amplifying said rlerived current, and means for combining said amplified a-rrival current and said amplified derived current to actuate said responsive device.

In witness whereof, I hereunto subscribe my name this 5th day of August A. D. 19I8.

ROBERT C. MATHES. 

